i want to write one, but i need your tips and advice as i've never written one before.

My complaint is thus:
I was supposed to fly from Edinburgh to Southampton on Thursday night with FlyBe. It was delayed for a while, then they announced we'd be diverted to Birmingham - a 3hr coach trip to Soton. All this meant that i didn't get home until 3am, 5 hours later than i should have been, and had to pay for a taxi home as it was too late for buses/trains.

so how can i write a letter that will get me results and get me my money back?